# for i in range(1,6):
#     if i == 3:
#         continue
#     print(i)

# for i in range(1,6):
#     if i == 3:
#         break
#     print(i)

#给定若干个数 ,求平均值
sum = 0#和
count = 0 #个数

while True:
    num = input("输入数字(分号代表输入结束:")
    if num == ';':
        break
    num = float(num)
    sum += num
    count += 1
print(sum / count)